2.9.1.10 - System Timer Low/High Read (Modes 10 & 11) [U6 Datasheet]
The LabJack U6 has a free-running internal 64-bit system timer with a frequency of 4 MHz. Timer modes 10 & 11 return the lower or upper 32-bits of this timer. An FIO line is allocated for these modes like normal, even though they are internal readings and do not require any external connections. This system timer cannot be reset, and is not affected by the timer clock.
If using both modes 10 & 11, read both in the same low-level command and read 10 before 11.
Mode 11, the upper 32 bits of the system timer, is not available for stream reads. Note that when streaming on the U6, the timing is known anyway (elapsed time = scan rate * scan number) and it does not make sense to stream the system timer modes 10 or 11.